The present invention relates to a method for cleaning pre-determinable surfaces of a heatable internal chamber, preferably of a combustion chamber, in which deposits form. The invention further relates to a blower lance which can be used for this method. A main area of application of the invention is the cleaning of power station boilers.
During in-service cleaning of clinkered or soiled heating surfaces in combustion chambers, water lance blowers which are arranged in an aperture are used to blow a compact water jet through the flames and the combustion chamber onto the wall opposite or to the side, and clean the walls by the shock effect of the water. Such water lance blowers are disclosed in DD 145 476 and DD 155 857. With this, the water lance implements a blowing pattern which can have the widest variety of geometry; For example, spirals (DD 145 476) or wave-form bands (DD 155 857). The water jet leaving the water lance blower then implements a cleaning pattern on the wall which the water jet strikes. The blowing path is controlled by control means for moving the water lance, which is mounted at its front area to a fixed point on the combustion chamber aperture and is guided on its rear bearing by means of path and/or time control of the lance guidance. In P 44 15 010.5, a control system is disclosed wherein with every working step a fixed reference point or site is started at, and thereby the same location for the initial position of the water lance for carrying out the blowing pattern is ensured. Any possible tolerances occurring in the control system are in this way levelled out so that no changes in the path occur. Different blowing patterns which also avoid apertures of, for example, burners and smoke recirculators, for the widest variety of surface areas and sizes of the wall surface to be cleaned, are allocated to a blower lance, and selectively commanded to perform the blowing operation.
It is further known from DE 195 19 748.8 A1, DE 195 19 780.1 A1 and DE 195 19 790.1 A1 to locally allocate the coordinates of the water lance positions to the geometrical arrangements of the wall surfaces. In this way each point of the wall surface struck by a geometric jet by the blower lance is allocated a blower lance coordinate.
There are also methods according to the prior art in which selection of the blowing pattern and of its blowing intensity is determined according to the degree of soiling of the wall surface. In DD 281 448, DD 281 452 and DD 281 468 methods are disclosed for control of water lance blowers and for sensing clinkered areas on heating surfaces in combustion chambers of coal powder furnaces. DD 281 448 describes a method for control of a water lance blower for cleaning heating surfaces, wherein reference images are generated by an optical probe which is connected to a camera and a measuring system. These are divided into fields using coordinates of the measuring system, and are characterised by signals. During the operation of the combustion chamber real-time images are generated and compared to the reference images. From the comparison, a clinkered area is determined and a command signal is produced from coordinates of known blowing patterns of the water lance blower, which controls the water lance blower for cleaning the clinkered area. A known blowing pattern can be determined using any manually controlled method for the water lance blower, while observing the water jet on a screen. DD 281 452 discloses a method wherein a water lance blower is steered to the clinkered area determined using known, memorised coordinates of blowing patterns of a water lance blower. In this way the area to be cleaned is delimited in terms of its area and periphery. In DD 281 468, the selection of the operation of the water lance blower is concentrated on selected cleaning areas according to the degree of soiling. In this case recording, summation and subsequent evaluation of the cleaning result is provided. In all these methods a geometrically defined water jet is assumed.
In an analogous manner to the method according to DD 281 468, in DE 41 39 838 the degree of emission of cleaned and soiled and clinkered furnace walls is measured by emission measuring means, compared with set values and from this commands are derived for the blowing rhythm and the blowing intensity with respect to the speed of the blown jet of a water lance blower. This solution is used for coals with thin, white, glossy or shining ashes or deposits. In accordance with DE 41 39 718 A1 and U.S. Pat. No. 4,539,588 an infra-red video image is generated for employing this method, which simultaneously compares the local radiation intensity of pre-determined soiled and clean furnace chamber measuring surfaces. This comparison is based on results of measurements by photo-detectors on preferred sites on the furnace chamber wall, which measure the local radiation intensity and display it on the monitor.
Known devices and methods for cleaning heating surfaces normally employ the position of the water lance blower when tracking its blowing pattern, in order to effect a connection between the surface to be cleaned and the water jet. This connection is based on geometrical considerations, wherein it is assumed that the target point of the water lance blower on the surface to be cleaned which can be derived by geometry coincides with the site of impact of the water jet. It has been attempted, as disclosed for example in DD 281 468, to memorise and later to employ a blowing pattern by observing a water jet.